1. Field of the Invention
The present invention relates generally to structures for providing electrical connections and/or interconnections for semiconductor devices. More particularly, the invention relates to ball grid array (BGA) packages, and conductive structures for connecting integrated circuits to ball grid arrays, including fine ball grid arrays (FBGA). The present invention also relates to methods of making electronic devices and the like, particularly tape-based methods of manufacturing semiconductor devices.
2. Discussion of the Related Art
Ball grid array packages are known in the art. In one such product, a resin material is located on the active surface of a semiconductor die. Solder balls are formed on top of the resin material. Wires connect the bond pads on the die to conductive traces patterned on the resin material. The wires extend through an opening in the resin material. The traces communicate signals from the wires to the solder balls. The resin material may be cut from a continuous tape after the device is otherwise assembled, according to a known tape-based manufacturing method.
The known devices and manufacturing processes have several disadvantages. Among other things, it would be advantageous to incorporate a stiffening or reinforcing structure into the ball grid array package described above without substantially increasing its overall size. The desired structure would produce a durable, easier to handle product, and it would make it practicable to employ thinner and/or more flexible material for the tape.
In addition, it would be advantageous to provide a means for dissipating or distributing heat from the semiconductor die without substantially increasing the size or complexity of the device.
In addition, as the size of ball grid array devices are reduced and the number and complexity of the required electrical interconnections are increased, it becomes increasingly difficult to produce a satisfactory conductive routing pattern on the resin material. Thus, it would be advantageous to provide a system for connecting the die to the ball grid array with a simplified conductive routing pattern.
The disadvantages of the prior art are overcome to a great extent by the present invention. The present invention relates to a semiconductor device with improved structural, thermal and/or electrical performance characteristics. The present invention also relates to a method of packaging a semiconductor die for use with an external device such as a circuit board.
According to one aspect of the invention, a device is formed of a semiconductor die, a ball grid array for communicating with an external device (such as a circuit board), and an electrically insulative layer. The insulative layer supports the ball grid array. That is, the insulative layer is located between the ball grid array and the die. An electrically conductive layer is located between the insulative layer and the die. The conductive layer, which may be made of metal, provides structural support (stiffness) and also dissipates heat away from the die. The ball grid array is electrically connected to the die by wires, traces and/or other conductive elements. At least some of these elements are also connected to the conductive layer. Consequently, the conductive layer may be used as a common ground plane.
According to another aspect of the invention, open areas are provided in the metal layer and the insulative layer to accommodate metal wires that are connected to the active surface of the die.
According to another aspect of the invention, the insulative layer may be cut from a tape structure. Conductive traces are patterned on the tape to route signals to the ball grid array. Some of the wires attached to the die are also attached to the conductive traces. Other wires may be attached to the metal ground plane and are insulated from the traces.
One or more via holes may be provided to connect the metal ground plane to the desired one or more balls of the ball grid array.
In a preferred embodiment of the invention, the fragile conductive elements are glob top encapsulated in resin.
According to another aspect of the invention, an electronic device is formed of a semiconductor die, a patterned film, and a metal grounding layer. The metal layer is located between the die and the patterned film.
The film has electrical conductors (for example, conductive traces, via holes and solder balls) for providing communication between the die and an external device. An advantage of the invention is that the package containing the die may have a small footprint and reduced height, if desired.
The present invention may be employed with a die that has centrally located bond pads. In addition, the invention may be used in perimeter pad devices. Thus, the metal layer may have a smaller surface area than the die. In another embodiment of the invention, the metal layer has peripheral portions that extend laterally outwardly beyond the edges of the die, for example to provide room for additional rows of solder balls and/or to provide increased heat dissipation. In another embodiment of the invention, the metal layer has a recess that receives or contains the die to provide increased stiffness, protection and/or heat dissipation. The present invention is not limited to the preferred embodiments described herein.
The invention also relates to a tape-based process for producing semiconductor devices. In a preferred embodiment of the invention, a tape structure is formed of electrically insulative tape, a succession of semiconductor dies attached to the tape, and stiff metal grounding layers. The metal layers are located between the dies and the tape. A corresponding succession of ball grid arrays, wires, or other electrical connection systems, may be located on the tape. Thus, according to the invention, semiconductor devices, workpieces and/or electronic components may be formed according to a tape-based process and subsequently separated from each other.
The invention also includes a multilayer structure as an alternative to the supporting insulative layer. This multilayer structure can comprise a plurality of insulative layers and circuitry layers in electrical connection with the die, the ball grid array, and/or ground layers. Also, within the multilayer structure, additional grounding or power planes can be provided. The multilayer structure provides improved routability in wiring circuitry and easier ground and power wiring. One or more via holes may also be provided to connect the ball grid array to underlying circuitry or conductive planes incorporated within the multilayer structure.
The above-noted features and aspects of the invention can be combined with one another in many ways. These and other features and advantages will become apparent to those of skill in the art from the following detailed description in conjunction with the below described drawings.